1. Field of the Invention
The present invention relates to a steering control device that carries out a steering assisting control with respect to a steering operation of a driver.
2. Description of the Related Art
Conventionally, a steering assisting control (assist control) that alleviates an operation force of a steering wheel of the driver by generating an assist torque at the time of the steering operation is known. This type of steering control device is, for example, disclosed in Japanese Patent Application Laid-open No. 2005-082119 and Japanese Patent Application Laid-open No. 2009-274692. If the steering operation is a turning operation, an impact load is generated when a steering angle becomes a maximum steering angle (at the time of end abutting). Thus, conventionally, for example, when the steering angle approaches the maximum steering angle, an attenuation torque of a dumping control is increased and the assist torque is reduced to suppress the impact load at the time of the end abutting. Furthermore, for example, in the steering control device described in Japanese Patent Application Laid-open No. 2005-082119, when the steering operation is the turning operation, the assist torque is reduced from the time of a steering angle before the maximum steering angle by a first predetermined angle (angle that is greater as the steering speed becomes greater) to reduce the impact load at the time of the end abutting. Moreover, in the steering control device, if the steering operation is a turning-back operation, the assist torque is increased to a maximum value (assist gain Ga=1) while the steering angle reaches a second predetermined angle (<first predetermined angle) from the maximum steering angle to ensure a satisfactory steering feeling at the time of the turning-back operation. The steering control device described in Japanese Patent Application Laid-open No. 2009-274692 detects that the steering angle reached a steering limit (maximum steering angle) when a change rate of the steering torque exceeds a predetermined value, and drive controls a motor in a direction an absolute value of the steering angle becomes small at the relevant time to reduce the impact load at the time of the end abutting.
In the conventional steering control device, the assist torque for the turning-back operation cannot be generated unless the turning-back operation is detected. Thus, the conventional steering control device does not switch from the dumping control of the turning operation to the dumping control of the turning-back operation until the turning-back operation is detected even if the turning-back operation is started from the maximum steering angle or the vicinity thereof, and hence the driver may feel a sense of uncomfortableness (i.e., catching feeling) at the instant the turning-back operation is started.
There is a need for a steering control device capable of suppressing the sense of uncomfortableness of the driver at the time of the turning-back operation.